System and method for programmably adjusting gain and frequency response in a 10-GigaBit ethernet/fibre channel system

ABSTRACT

Aspects of the invention may provide a method and system for adjusting a gain and/or a frequency response of an input signal for a multimode PHY device. A signal divider may apportion the input signal into a gain adjustment signal and/or an equalization adjustment signal upon receipt of the input signal. A signal adjuster coupled to the signal divider may adjust a gain of the apportioned gain adjustment signal within the multimode PHY device. An equalizer coupled to the signal divider may be configured to equalize the equalization adjustment signal within the multimode PHY device. A summer coupled to the equalizer and signal adjuster may be adapted to sum the adjusted adjustment signal and the equalized equalization adjustment signal within the multimode PHY device to create an output equalized signal having a desired gain and/or frequency response.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application makes reference to, claims priority to and claims thebenefit of U.S. Provisional Patent Application Ser. No. 60/402,120 filedon Aug. 7, 2002.

This application also makes reference to U.S. Pat. No. 6,424,194, U.S.application Ser. No. 09/540,243 filed on Mar. 31, 2000, U.S. Pat. No.6,389,092, U.S. Pat. No. 6,340,899, U.S. application Ser. No. 09/919,636filed on Jul. 31, 2001, U.S. application Ser. No. 09/860,284 filed onMay 18, 2001, U.S. application Ser. No. 10/028,806 filed on Oct. 25,2001, U.S. application Ser. No. 09/969,837 filed on Oct. 1, 2001, U.S.application Ser. No. 10/159,788 entitled “Phase Adjustment in High SpeedCDR Using Current DAC” filed on May 30, 2002, U.S. application Ser. No.10/179,735 entitled “Universal Single-Ended Parallel Bus; fka, Using1.8V Power Supply in 0.13 MM CMOS” filed on Jun. 21, 2002, and U.S.application Ser. No. 60/402,090 entitled “System and Method forImplementing a Single Chip Having a Multiple Sub-layer PHY” filed onAug. 7, 2002.

All of the above stated applications are incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

Embodiments of the present application relate generally to opticalnetworking hardware, and more particularly to a system and method forperforming on-chip synchronization of system signals.

High-speed digital communication networks over copper and optical fiberare used in many network communication and digital storage applications.Ethernet and Fiber Channel are two widely used communication protocols,which continue to evolve in response to increasing need for higherbandwidth in digital communication systems. The Open SystemsInterconnection (OSI) model (ISO standard) was developed to establishstandardization for linking heterogeneous computer and communicationsystems. It describes the flow of information from a softwareapplication of a first computer system to a software application of asecond computer system through a network medium.

The OSI model has seven distinct functional layers including Layer 7: anapplication layer; Layer 6: a presentation layer; Layer 5: a sessionlayer; Layer 4: a transport layer; Layer 3: a network layer; Layer 2: adata link layer; and Layer 1: a physical layer. Importantly, each OSIlayer describes certain tasks that may be necessary for facilitating thetransfer of information through interfacing layers and ultimatelythrough the network. Notwithstanding, the OSI model does not describeany particular implementation of the various layers.

OSI layers 1 to 4 generally handle network control and data transmissionand reception. Layers 5 to 7 handle application issues. Specificfunctions of each layer may vary depending on factors such as protocoland interface requirements or specifications that are necessary forimplementation of a particular layer. For example, the Ethernet protocolmay provide collision detection and carrier sensing in the physicallayer. Layer 1, the physical layer, is responsible for handling allelectrical, optical, opto-electrical and mechanical requirements forinterfacing to the communication media. Notably, the physical layer mayfacilitate the transfer of electrical signals representing aninformation bitstream. The physical layer may also provide services suchas, encoding, decoding, synchronization, clock data recovery, andtransmission and reception of bit streams. In high bandwidthapplications having transmission speeds of the order of Gigabits,high-speed electrical, optical and/or electro-optical transceivers maybe used to implement this layer.

As the demand for higher data rates and bandwidth continues to increase,equipment capable of handling transmission rates of the order of 10Gigabits and higher is being developed for high-speed networkapplications. Accordingly, there is a need to develop a 10 Gigabitphysical layer device that may facilitate such high-speed serial dataapplications. For example, XENPAK multi-source agreement (MSA) defines afiber optical module that conforms to the well-known IEEE standard for10 Gigabit Ethernet (GbE) physical media dependent (PMD) types. In thisregard, XENPAK compatible transceivers may be used to implement thephysical layer. Notwithstanding, there is a need for transceivers, whichare necessary for implementing 10 Gigabit physical layer applications.The well-known IEEE P802.3ae draft 5 specifications describes thephysical layer requirements for 10 Gigabit Ethernet applications and isincorporated herein by reference in its entirety. In a XENPAK module,since the 10 Gbps signal is connected locally to the optical components,the 10 Gbps signals do not have to travel long distances. In this case,the frequency response of a receiver in the physical layer should have aflat frequency response to preserve the integrity of the information inthe electrical signals being converted from optical to electricalsignals. An optical-based transceiver, for example, may include variousfunctional components which may implement tasks such as clock datarecovery, clock multiplication, serialization/deserialization,encoding/decoding, electrical/optical conversion, descrambling, mediaaccess control (MAC), controlling, and data storage.

In Fibre channel applications, system manufacturers prefer to use smallform factor optical modules such as XFP instead of XENPAK modules,because of the cost savings associated with using multiple ports. In thecase of XFP modules, 10 Gb/s signal may travel across the system using acopper (FR4) connection to reach the module. As high-speed communicationsignals such as 10 Gbps are transmitted over a network, the signal maybecome attenuated. For a copper media, typically, high frequencycomponents of a communication signal are attenuated more than the lowerfrequency components. Existing high-speed data receivers attempt to dealwith this high frequency attenuation by providing an equalizationelement that amplifies the incoming signal and amplifying the higherfrequency signal components more than the lower frequency signalcomponents. Since Ethernet and Fibre Channel systems exhibit differentsignal attenuation properties, an optimal equalization element for anEthernet system will have different characteristics than an optimalequalization element for a Fibre Channel system.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

Aspects of the invention may provide a method and system for adjusting again and/or a frequency response of an input signal for a multimode PHYdevice. The method may include the step of apportioning the input signalinto a gain adjustment signal and/or an equalization adjustment signal.Apportionment of the input signal may be achieved within the multimodePHY device. Accordingly, a gain for the gain adjustment signal may beadjusted within the multimode PHY device. The equalization adjustmentsignal may also be equalized within the multimode PHY device. A summermay subsequently be adapted to sum or combine the adjusted gainadjustment signal and the equalized equalization adjustment signal tocreate an output equalized signal having a desired gain and/or frequencyresponse.

The apportioned gain adjustment signal may include low frequencycomponents of the input signal, while the apportioned equalizationadjustment signal may include high frequency components of the inputsignal. The apportioning step may further include the step of selectinga determined portion of the input signal that will comprise the gainadjustment signal and/or the equalization signal. The determined portionof the input signal may be the whole of the input signal or a fractionalportion of the input signal. The adjusting step may be programmablyachieved through one or more bits and/or registers.

The adjustment step may further include the step of amplifying the gainof some or all of the low frequency components that comprise theapportioned gain adjustment signal. Amplification may be achievedequally over all of the low frequency components of the apportioned gainadjustment signal. The equalizing step may further include the step ofamplifying the gain of some or all of the high frequency components thatcomprise the apportioned equalization adjustment signal. The inputsignal may include signal components from at a 10 GigaBit Ethernetoperation mode and/or a Fibre channel operation mode. The apportioningstep may also include the step of apportioning the input signal so thatthe gain adjustment signal and the equalization adjustment signal areequivalent to the input signal.

In another embodiment of the invention, a system for adjusting at leastone of a gain and a frequency response of an input signal for amultimode PHY device may be provided. The system may include a signaldivider for apportioning the input signal into a gain adjustment signaland/or an equalization adjustment signal upon receipt of the inputsignal. A signal adjuster coupled to the signal divider may adjust again of the apportioned gain adjustment signal within the multimode PHYdevice. An equalizer coupled to the signal adjuster may be configured toequalize the equalization adjustment signal within the multimode PHYdevice. A summer coupled to the equalizer and signal adjuster may beadapted to sum the adjusted gain adjustment signal and the equalizedequalization adjustment signal within the multimode PHY device to createan output equalized signal.

The apportioned gain adjustment signal may include low frequencycomponents of the input signal. The apportioned equalization adjustmentsignal may include high frequency components of the input signal. Thesignal divider may further include a selector configured for selecting adetermined portion of the input signal that will comprise the gainadjustment signal and the equalization adjustment signal. The selectormay be configured to select the determined portion of the input signalthat may be the whole of the input signal or a fraction of the inputsignal.

The signal adjuster may further include a programmable selector that maybe adapted for programmably selecting the determined portion of theinput signal that will comprise the gain adjustment signal and theequalization signal. The adjuster may further include an amplifier,which may be configured for amplifying a gain of some or all of the lowfrequency components of the apportioned at least gain adjustment signal.The amplifier may be configured to equally amplifying the gain of someor all of the low frequency components that comprise the apportionedgain adjustment signal. The equalizer may further include an amplifierfor amplifying the gain of some or all of the high frequency componentscomprising the apportioned equalization adjustment signal. The inputsignal may have signal components from a 10 Gigabit Ethernet operationmode and/or a Fibre channel operation mode. Finally, the signal dividermay further include an apportioner which may be configured forapportioning the input signal so that the gain adjustment signal and theequalization adjustment signal are equivalent to the input signal.

Another embodiment of the invention provides a method for adjusting atleast a gain and/or a frequency response of an input signal for amultimode PHY device. The method may include adjusting a gain of atleast a portion of the input signal within the multimode PHY deviceafter receipt of the input signal. At least a remaining portion of theinput signal may be equalized within the multimode PHY device. Theadjusted at least a portion of the input signal and the equalized atleast a remaining portion of the input signal may be summed within themultimode PHY device to create an output equalized signal having adesired gain and frequency response. The adjusted at least a portion ofthe input signal may include low frequency components of the inputsignal, and the equalized at least a remaining portion of the inputsignal may include high frequency components of the input signal. Theadjusting step may further include the step of amplifying the gain of atleast a portion of the low frequency components and equally amplifying again of at least a portion of the low frequency components.

Another embodiment of the invention further provides a system foradjusting at least one of a gain and a frequency response of an inputsignal for a multimode PHY device. The system may include at least oneadjuster adapted to adjust a gain of at least a portion of the inputsignal within the multimode PHY device. At least one equalizer may beadapted to equalize at least a remaining portion of the input signalwithin the multimode PHY device. At least one summer may be adapted tosum the adjusted at least a portion of the input signal and theequalized at least a remaining portion of the input signal within themultimode PHY device to create an output equalized signal having adesired gain and frequency response.

The adjusted at least a portion of the input signal may include lowfrequency components of the input signal, and the equalized at least aremaining portion of the input signal may include high frequencycomponents of the input signal. The adjuster may further include atleast one controller adapted to control amplification of the gain of atleast a portion of the low frequency components. The at least onecontroller may be adapted to control equal amplification of the gain ofthe at least a portion of said low frequency components. The at leastone controller may be further adapted to control amplification of the atleast a portion of the high frequency components of the input signal.The at least one controller may be further adapted to control adjustmentof the at least a portion of the high frequency components of the inputsignal independent of the at least a portion of the low frequencycomponents. The input signal may include signal components from at leastone of a 10 GigaBit Ethernet operation mode and a Fibre channeloperation mode.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary transceiver module inaccordance with an embodiment of the invention.

FIG. 2 is a block diagram of an exemplary single-chip multimodemulti-sublayer PHY used in the transceiver module of FIG. 1 inaccordance with an embodiment of the invention.

FIG. 3 is a schematic block diagram illustrating an embodiment of thesingle-chip multimode multi-sublayer PHY of FIG. 2 in accordance with anembodiment of the invention.

FIG. 4 is a plot illustrating a frequency response of an exemplarycommunication signal communicated over a high-speed network.

FIG. 5 is a plot illustrating a typical equalization profile that may beutilized to equalize an attenuated communication signal.

FIG. 6 is a plot illustrating an increase in signal amplitude acrossfrequency components that may comprise the signal.

FIG. 7 a is a block diagram of an exemplary signal equalization elementaccording to an embodiment of the present invention.

FIG. 7 b is an exemplary block diagram of an equalization element thatutilizes a flat gain stage and a high pass filter stage in accordancewith an embodiment of the invention.

FIG. 8 is a plot illustrating exemplary equalization profiles accordingto an embodiment of the invention.

FIG. 9 is plot for exemplary equalization profiles in accordance with anembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram of an exemplary transceiver module 100 inaccordance with an embodiment of the invention. Referring to FIG. 1,there is illustrated a computer system 105, a medium access control(MAC) controller 120, a MAC controller interface 115, an optical network110, a single-chip multimode multi-sublayer PHY device 130, anelectrically erasable programmable read only memory (EEPROM) 140, a PMDtransmitter 125 a and a PMD receiver 125 b. PMD transmitter 125 a andPMD receiver 125 b may be integrated into a single PMD 125 such as achip or IC, although the invention is not limited in this regard.Transceiver module 100 may be an integrated device, which may includethe single-chip multimode multi-sublayer PHY device 130, the EEPROM 140,the optical transmitter 125 a and the optical receiver 125 b. Computersystem 105 may interface with MAC controller 120 through MAC controllerinterface 115 and may communicate with the optical network 110 throughthe transceiver module 100. The single-chip multimode multi-sublayer PHYdevice 130 may also be referred to as a multimode PHY for brevity.

Transceiver module 100 may be configured to communicate, namely transmitand receive, data between computer system 105 and optical network 110.The data transmitted and/or received may be formatted in accordance withthe well-known OSI protocol standard. The OSI model partitionsoperability and functionality into seven distinct and hierarchicallayers. Generally, each layer in the OSI model is structured so that itmay provide a service to the immediately higher interfacing layer. Forexample, layer 1 may provide services to layer 2 and layer 2 may provideservices to layer 3. The data link layer, layer 2, may include a MAClayer whose functionality may be handled by a MAC controller 120. Inthis regard, MAC controller 120 may be configured to implement thewell-known IEEE 802.3ae Gigabit Ethernet protocol.

In the arrangements of FIG. 1, the computer system 105 may representlayer 3 and above, the MAC controller 120 may represent layer 2 andabove and the transceiver module 100 may represent layer 1. The computersystem 105 may be configured to build the five highest functional layersfor data packets that are to be transmitted over the optical network110. Since each layer in the OSI model may provide a service to theimmediately higher interfacing layer, the MAC controller 120 may providethe necessary services to the computer system 105 to ensure that packetsare suitably formatted and communicated to the transceiver module 100.During transmission, each layer may add its own header to the datapassed on from the interfacing layer above it. However, duringreception, a compatible device having a similar OSI stack may strip offthe headers as the message passes from the lower layers up to the higherlayers.

The transceiver module 100 may be configured to handle all the physicallayer requirements, which may include, but is not limited to,packetization, serialization/deserialization (SERDES) and data transfer.Transceiver module 100 may operate at a plurality of data rates, whichmay include 10 Gbps. Data packets received by the transceiver module 100from MAC controller 120 may include data and header information for eachof the above six functional layers. The transceiver module 100 may beconfigured to encode data packets that are to be transmitted over theoptical medium of the optical network 110. The transceiver module 100may also be configured to decode data packets received from the opticalnetwork 110.

The MAC controller 120 may interface with the single-chip multimodemulti-sublayer PHY 130 of the transceiver module 100 through a 10 GbpsEthernet attachment unit interface (XAUI) 135. The XAUI 135 may be a lowpin count device having a self-clocked bus, which directly evolved fromlower data rate protocols. The XAUI may function as an extenderinterface for a 10 Gigabit media independent interface (XMGII). In thisregard, MAC controller 120 may also include an XGMII extender sublayer(XGXS) interface 150 and a reconciliation sublayer (RS) interface 145.MAC controller 120 may include an integrated link management (MGMT)interface 155 that may facilitate communication between MAC controller120 and a management data input/output (MDIO) interface of thesingle-chip multi-sublayer PHY 130.

In one aspect of the invention, XAUI 135 may be configured to utilize aplurality of serial data lanes on each of its receive 135 a and transmit135 b interfaces to achieve compatible 10 GbE operational speeds.Notably, the XAUI 135 may be configured as two, 4-bit interfaces, eachwith four serial lines, thereby achieving a throughput of about 10 Gbps.In accordance with the embodiments of FIG. 1, XAUI 135 a may beconfigured to transmit data from the MAC controller 120 to thesingle-chip multimode multi-sublayer PHY 130. Additionally, XAUI 135 bmay be configured to transmit data from the single-chip multimodemulti-sublayer PHY 130 to the MAC controller 120.

The single-chip multimode multi-sublayer PHY 130 may support multiplemodes of operation. In this regard, the single-chip multimodemulti-sublayer PHY 130 may be configured to operate in one or more of aplurality of communication modes. Each communication mode may implementa different communication protocol. These communication modes mayinclude, but are not limited to, 10 GbE, fibre channel and other similarprotocols. The single-chip multimode multi-sublayer PHY 130 may beconfigured to operate in a particular mode of operation uponinitialization or during operation.

The single-chip multimode multi-sublayer PHY 130 may also include afully integrated serialization/deserialization device, which may also beconfigured to operate at speeds of 10 Gbps. During transmission, thesingle-chip multimode multi-sublayer PHY 130 may serialize the datareceived over the 4-bit XAUI 135 a and transmit the data in a formatsuch as a single 10 Gbps stream via the PMD transmitter 125 a. Duringreception, the single-chip multimode multi-sublayer PHY 130 mayde-serialize a single 10 Gbps signal received by the PMD Rx 125 b andtransmit the data in a format such as a 4-bits×3.125 Gbps datastreamover XAUI 135 b.

The PMD 125 may include at least one PMD transmitter 125 a and at leastone PMD receiver 125 b. In operation, PMD 125 may be configured toreceive data from and transmit data to the optical network 110. The PMDtransmitter 125 a may transmit data originating from the computer system105 over the optical network 110. The PMD receiver 125 b may receivedata destined for computer system 105 from the optical network 110 andtransmit the data to the computer system 105. The PMD 125 may also beconfigured to function as an electro-optical interface. In this regard,electrical signals may be received by PMD transmitter 125 a andtransmitted in a format such as optical signals over the optical network110. Additionally, optical signals may be received by PMD receiver 125 band transmitted as electrical signals to the computer system 105. In oneaspect of the present invention, for Ethernet operation, the 10 Gigabitdata rate may actually be 10.3125 Gbps and for Fibre Channel operation,the 10 Gigabit data rate may actually be 10.516 Gbps, although theinvention is not limited in this regard.

The transceiver module 100 may also include an EEPROM 140. Thesingle-chip multimode multi-sublayer PHY 130 may be coupled to EEPROM140 through an interface such as a serial interface or bus. EEPROM 140may be programmed with information which may include parameters and/orcode that may effectuate the operation of the single-chip multimodemulti-sublayer PHY 130. The parameters may include configuration dataand the code may include operational code such as firmware, although itshould be recognized that the information is not limited in this regard.

FIG. 2 is a block diagram of an exemplary single-chip multimodemulti-sublayer PHY 130 used in the transceiver module of FIG. 1 inaccordance with an embodiment of the invention. Referring now to FIG. 2,the single-chip multimode multi-sublayer PHY 130 may include a XAUIreceiver 205, a XAUI transmitter 210, a PMD transmitter 215, and a PMDreceiver 220. The single-chip multimode multi-sublayer PHY 130 mayfurther include a digital core 225 which may have one or moreperipherals, for example, peripheral #1 225 a and peripheral #2 225 b.The digital core 225 may include an XGXS PCS sublayer and a PMD PCSsublayer. A XAUI TX/RX sublayer may include the XAUI transmitter 210 andXAUI receiver 205 sections. A PMD TX/RX sublayer may include the PMDtransmitter 215 and PMD receiver 220 sections. Various sublayers of thesingle-chip multimode multi-sublayer PHY 130 may be fabricated in 0.13micron CMOS technology.

In operation, digital core 225 may be configured to serialize anddeserialize (SERDES) received data. Data from the XAUI 135 a may bereceived at XAUI receiver 205, serialized by the digital core 225, andtransmitted as a single 10 Gbps datastream by the PMD transmitter 215.This may be considered the transmit path. Data from the optical PMDreceiver 125 b may be received at PMD receiver 220, deserialized by thedigital core 225, and transmitted as, for example, 4-bit×3.125 Gbpsstreams by the XAUI receiver 210. This may be considered the receivepath.

FIG. 3 is a schematic block diagram illustrating an embodiment of thesingle-chip multimode multi-sublayer PHY 130 of FIG. 2 in accordancewith an embodiment of the invention. FIG. 3 may provide a more detailedschematic block diagram of the singlechip multimode multi-sublayer PHY130 of FIG. 2, which may be used in the transceiver module 100 ofFIG. 1. Referring to FIG. 3, the single-chip multimode multi-sublayerPHY 130 may include three main functional blocks. Namely, a transmitblock 310, a receive block 340, and a management and control block 370.Clock interfaces may be provided for configuring the XAUI and PMDinterfaces for operating in a synchronous mode or an asynchronous mode.

The transmit block 310 may include a clock multiplier unit (CMU) andserializer block 316, a gearbox 328, an encoder scrambler block 326, atleast one elastic FIFO 324, one or more lane alignment FIFOs 322, one ormore lane detect lane sync decoders 320, and one or more DLL anddeserializer 318. The receive block 340 may include a CDR deserializer348, a gearbox 350, a synchronizer descrambler decoder block 352, atleast one elastic FIFO 354, a randomizer 356, one or more encoders 358,one or more serializers 360, and a CMU 346. The management and controlblock 370 may include a management registers and control interface block372 and an optics and control status block 374.

In operation, the transmit block 310 may be configured to receive dataformatted in a format such as a 4-lane 3 Gigabit data at the XAUIreceivers 312 and reformat the received data in a format suitable for 10Gigabit serial transmission at the PMD differential CML drivers 314. ThePMD CMU and serializer 316 in the PMD TX/RX sublayer may be configuredto be phase-locked (PL) to a reference clock such as an externalreference clock. In one aspect of the invention, each of the XAUIreceivers 312 may be configured to handle one lane of received data. Inthis regard, each of the XAUI receivers 312 in the XAUI TX/RX sublayermay include an internal delayed-lock loop (DLL), which may be adapted tosynchronize the sampling clock signal to any incoming data signal.

A PLL is an electronic circuit that may be configured to control andfrequency source such as an oscillator, so that it maintains a constantphase angle relative to a reference signal. The reference signal may beextracted from a received signal. PLLs may be used for applications suchas, bit synchronization, symbol synchronization, and coherent carriertracking. An exemplary digital PLL (DPLL) circuit may include a serialshift register, a phase corrector circuit and a local clock signal. Theserial shift register may be configured to receive digital inputsamples. The digital input samples may be extracted from the receivedsignal. Preferably, the local clock signal may be stable enough tosupply clock pulses that may drive the serial shift register. The phasecorrector circuit may be adapted to take the local clock signal andregenerate a stable clock signal that may be in phase with the receivedsignal. In this regard, the phase corrector circuit may be configured toslowly adjust the phase of the regenerated clock signal to match thereceived signal. The regenerated clock signal may be utilized to samplethe received data and determine the value of each received bit.

In operation, the received signal may be sampled at the local clockrate. This may generally be a multiple of the nominal regenerated clockfrequency such as 32 times. Each sample, whether (0) or one (1), may beshifted into the shift register. The need to adjust the phase may bedetermined by viewing a set of samples of the received signal. At eachregenerated bit period, the shift register may be consulted. If thecenter of the received bit lies at the center of the shift register, thetwo clocks may be deemed to be in phase and no compensation oradjustment may be necessary. If the regenerated clock signal lags thereference signal, then the phase adjuster may provide compensation byadvancing the regenerated clock. If the regenerated clock signal leadsthe reference signal, then the phase adjuster may provide compensationby retarding the regenerated clock.

Accordingly, after synchronization, a 3 Gigabit sampling clock signal,for example, may be configured to sample the data signal in the centerof a data eye pattern. In this arrangement, a phase relationship betweenthe edge transitions of the data signal and those of the sampling clocksignal may be determined and compared by a phase/frequencydiscriminator. Output pulses from the discriminator may indicate thedirection that may be required for adequately correcting a phase of thesignal. Additionally, a loop filter may be configured to smooth anypulses that may occur in the signal. An output signal generated by theloop filter may be adapted to control one or more internal phaseinterpolators, which may be used to generate the sampling clock. TheXAUI CMU 316 may be adapted to function as a phase locked loop (PLL)within the XAUI TX/RX sublayer and may be configured to generate clocksfor internal DLL phase interpolations.

The single-chip multimode multi-sublayer PHY 130 may include one or moreloss-of-signal (LOS) detect circuits. In one embodiment of theinvention, the single-chip multimode multi-sublayer PHY 130 may beconfigured to include a loss-of-signal (LOS) detect circuit for eachXAUI DLL within the XAUI TX/RX sublayer. In this regard, the LOS detectcircuits may be configured to monitor and detect data presence at theXAUI receiver inputs 312. A minimum single-ended input signal swing maybe used for a valid phase lock condition although the invention is notso limited. The status of each individual LOS detector may be determinedfrom one or more bits and/or internal register of the single-chipmultimode multi-sublayer PHY 130.

In one aspect of the present invention, the XAUI serial inputs 312 forthe transmit block 310 of the XAUI TX/RX sublayer may be AC-coupled. Inthis regard, AC coupling may prevent voltage drops across input devicesof the single-chip multimode multi-sublayer PHY 130 whenever the inputsignals may be sourced from a higher operating voltage device. In a casewhere DC coupling may be used, it may be necessary to ensure that theinput signals do not exceed certain VDD levels. Additionally, noise dueto overshooting and undershooting of transient currents may also beappropriately handled.

Each XAUI serial data stream for the XAUI serial inputs 312 may bedeserialized by one of the DLL and de-serializers 318 integrated withinthe XAUI TX/RX sublayer. DLL and de-serializers 318 may include one ormore serial-to-parallel converters that may be adapted to create, forexample, a 10-bit word from the receive serial input data stream. DLLoutput clocks may be provided and configured to drive theserial-to-parallel converters and/or DLL and de-serializer 318. Innormal operation, the DLL may recover the clock from the input datasignal. In a case where no data is present, the clock may be recoveredfrom an internal reference clock. In this regard, the output may be sentto the XGXS PCS sublayer in the digital core 225 (FIG. 1).

The XGXS PCS sublayer may include a synchronization (SYNC) sub-block.The sync acquisition sub-block in the XGXS PCS sublayer may beconfigured to perform code group synchronization, for example, on theincoming 10-bit bytes resulting from the DLL and de-serializer 318. Atwo-stage 10-bit shift register may be configured to recognize a validboundary of the input data stream. For example, the two-stage 10-bitshift register may be configured to recognize a /COMMA/ (K28.5) codegroup, which may be used to indicate a valid data boundary. In thiscase, upon detection of a single /COMMA/, or other suitable boundary, atleast one of the 8B/10B decoders 320 may be enabled. Upon detection offour /COMMA/ code groups without any intervening invalid code grouperrors, a sync acquisition may be declared.

The 8B/10B decoders 320 may be configured to perform error checks, whichmay include, but are not limited to, illegal code checks, disparitychecks and invalid code checks. In one aspect of the invention, both anillegal code and a running disparity error may cause an invalid code. Inthis case, an invalid code counter, which may be maintained forperformance monitoring, may be incremented. The invalid code counter maybe cleared upon a read access or other suitable method. The 8B/10Bdecoders 320 may also be configured to handle certain decoding taskswithin the XGXS PCS sublayer.

A difference between the number of 1's and 0's in a block of data may becharacterized as a running disparity (RD). A RD may be regarded as beingpositive when there are more ones (1s) than zeros (0s) and negative whenthere are more zeros (0s) than ones (1s). In an exemplary encodingscheme, each encoded 10-bit word may be assigned a RD of 0, +2, or −2,in order to ensure a high bit transition density for reliable clockrecovery. Additionally, the RD encoding may be alternated for DCbalancing. The balancing may be achieved by maintaining an equal numberof ones (1s) and zeros (0s). Upon receipt of an invalid code, a decodermay replace the invalid code with an error code (/E/) K30.7, and mayincrement the invalid code counter. Upon receipt of a legitimate errorcode, /E/, one or more of the 8B/10B decoders 320 may pass the error tothe XGXS PCS sublayer without incrementing the invalid counter.

Each of the outputs of the 8B/10 decoders 320 may be coupled to acorresponding one of a plurality of lane alignment FIFOs 322. Each laneassignment FIFO 322 may have a corresponding read and write pointer. Inoperation, at the start of lane alignment by each of, for example, fourlane alignment FIFOs 332, the four Lane Alignment FIFO write-pointerswithin the XGXS PCS sublayer may be enabled upon detection of aboundary, such as an /A/. The FIFOs common read-pointer may be enabledwhen all four XAUI lanes have detected /A/. Upon detection of an /A/ inone lane without /A/ detections in the other three lanes within aprogrammable window or skew budget, all FIFOs may be reset, therebyforcing the lane alignment process to start over again. The laneAlignment FIFOs 322 may be adapted to support lane skew compensation of,for example, 5 byte-clocks. Notwithstanding, in accordance with theinvention, the single-chip multimode multi-sublayer PHY 130 may permitabout 21 external UIs in compliance with the IEEE 802.3ae standard.

The PMD PCS sublayer may utilize a transmission code to improve thetransmission characteristics of information, which may be transferredacross a communication link. The transmission code may also supporttransmission of control and data characters. In this regard, thesingle-chip multimode multi-sublayer PHY 130 may be configured tosupport 64B/66B encoding as defined by IEEE 802.2ae clause 49 fortransmission code. Advantageously, this may ensure the existence ofsufficient synchronization information in bit stream to make clockrecovery more robust at the receiver.

The output of the lane alignment FIFOs 322 may be coupled to at leastone elastic FIFO 324. The output of the at least one elastic FIFO 324may be coupled to an encoder scrambler block 326. The output of theencoder scrambler block 326 may be coupled to a TX gearbox 328 embeddedin the PMD PCS sublayer. The fame synchronizer function of the encoderscrambler block 326 may be configured to encode, for example, a 66-bitframe boundary within the received data. This may permit the famesynchronizer function of the frame synchronizer descrambler decoderblock 352 to lock to a 66-bit block using a sync header of the 66-bitframe boundary. In one aspect of the invention, the encoder scramblerblock may be configured to encode the blocks of data in accordance withthe IEEE 802.3ae specification.

The TX gearbox 328 in the PMD PCS sublayer may be adapted to function asa buffer that may convert, for example, 64-bit data to 66-bit data formore efficient serialization. In one aspect of the invention, the TXgearbox 328 may be configured to receive 64-bit data from the scrambler344 and a 2-bit sync from a type generator at a frequency such as 156.25MHz. The TX gearbox 328 may produce a 66-bit data output at a frequencysuch as 322.265 MHz to the PMD CMU and serializer 316 within the PMDTX/RX sublayer. A register bank may be employed which may be accessed ina circular manner. In this regard, data may be read out of the TXgearbox 328 using an internally generated clock signal such as a 322.265MHz clock. The data may be converted to a 10 Gigabit serial streamwithin PMD TX/RX sublayer and driven off-chip by the differential CMLoutputs 314. In one embodiment of the invention, bit zero (0) of framezero (0) or the least significant bit (LSB), may be shifted out first.The PMD CMU and serializer 316 within the PMD TX/RX sublayer may have aPLL that may be configured to generate a 10 Gigabit clock by multiplyingfor example, the internal 156.25 MHz reference clock.

The single chip multimode multi-sublayer PHY 130 may also include a lockdetect circuit. The lock detect circuit may be configured to monitor thefrequency of any internal VCO. The status of the lock detect may beindicated by one or more bits and/or registers, for example bit zero (0)of an analog transceiver status register (ATSR). A register bit such asa P_LKDTCMU bit may also be configured to transition to a high statewhenever the PMD CMU PLL is phase locked. The CMU lock detect signal mayalso be provided as an output status at the PCMULK pin 348.

The CML serial outputs 314, namely PCOP, PCON, PDOP and PDON may beAC-coupled or DC-coupled. A source voltage of about +1.8V may power theCML outputs 314. Various pins on single-chip multimode multi-sublayerPHY 130 may be configured to provide power to the PCOP, PCON, PDOP andPDON CML serial outputs 314. The PCOP, PCON, PDOP and PDON CML serialoutputs 314 may be adapted as high-speed CML outputs that may include adifferential pair designed to drive, for example, a 50Ω transmissionline. An output driver may be back terminated to, for example, a 50Ωon-chip resistor, in order to provide snubbing of any signalreflections.

Management and control block 370 may include suitable control logic andcircuitry for controlling management functions of the single-chipmultimode multi-sublayer PHY 130. For example, management registers andcontrol interface block 372 may include one or more registers that maybe configured to deactivate the optical transmitter in the optical PMD125 a. Deactivation may be achieved, for example, by transmitting aconstant logical low level (0) at the output of PMD 125. A polarity ofPDIP, PDIN 344 and PDOP, PDON 342 may be reversed in order toaccommodate difficult printed circuit board (PCB) layouts. In thisregard, each differential signal pair may have its own polarity controlbit in the PMD/Optics Digital Control Register 374.

In accordance with the invention, the single-chip multimodemulti-sublayer PHY 130 may comply with the jitter specificationsproposed for 10 Gbps Ethernet equipment as defined by IEEE 802.3aestandards. Furthermore, the reference clock characteristics may also beadapted to adhere to this standard although the invention is not solimited.

In operation, receiver block 340 may be configured to receive 10 Gigabitserially formatted PMD data. Upon receipt of the serially formatteddata, receiver block 340 may reformat the data for transmission in asuitable format such as a 4-lane 3 Gigabit format by XAUI transmitter210 (FIG. 2). One of the 3 Gigabit CMU clocks, for example, CMU 346 inthe XAUI TX/RX sublayer may be adapted to retune some or all of the XAUItransmitters. The XAUI CMU 346 in the XAUI TX/RX sublayer may bephase-locked to, for example, an external reference clock.

The PMD clock and data recovery (CDR) and serializer 348 within the PMDTX/RX sublayer may be configured to generate a clock signal having, forexample, the same frequency as the incoming data bit rate (10 Gigabitrate) at the CML serial data inputs, PDIP and PDIN 344. In this regard,the clock may be phase-aligned by a PLL so that it samples the data inthe center of the data eye pattern.

The phase relationship between the edge transitions of the data andthose of the generated clock may be compared by a phase/frequencydiscriminator. In this arrangement, a phase relationship between theedge transitions of the data signal and those of the sampling clocksignal may be determined and compared by a phase/frequencydiscriminator. Output pulses from the discriminator may indicate thedirection that may be required for adequately correcting a phase of thesignal. Additionally, a loop filter may be configured to smooth anypulses that may occur in the signal. An output signal generated by theloop filter may be adapted to control one or more internal phaseinterpolators, which may be used to generate the sampling clock. Theoutput of the loop filter may control the frequency of the VCO, whichmay generate the recovered clock. Frequency stability without incomingdata may be guaranteed, for example, by an internal reference clock. Inthis case, the internal reference clock may provide an appropriate clockto which the PLL may lock whenever there is a loss of data signal.

The single-chip multimode multi-sublayer PHY 130 may also include a lockdetect circuit that may be adapted to monitor the 10 Gigabit frequencyof any internal VCO within the PMD TX/RX sublayer. In one embodiment ofthe invention, the frequency of the incoming data stream may beconfigured to be within, for example, ±100 ppm of the 10 Gigabit datastream for the lock detector to declare a signal lock. The lock detectstatus may be indicated by one or more bits and/or registers, forexample, bit zero (0) of the ATSR. In this case, the P_LKDTCDR bit maybe configured to transition to a high state whenever the PMD CDR islocked to the incoming data. The CDR lock detect signal may also beprovided as an output status at the PCDRLK pin 364.

The single-chip multimode multi-sublayer PHY 130 may also include a LOSdetect circuit that may be configured to monitor the integrity of theserial receiver data path in the PMD TX/RX sublayer. A peak detector maybe configured to look for a minimum amplitude swing in the signal. In acase where there is no serial data input present, a bit such as a LOS_Pbit in the ATSR may be set to zero (0). In one aspect of the invention,during operation, the CDR and deserializer block 348 may attempt to lockto the reference clock whenever the signal level falls below a minimumamplitude swing and a bit such as a LOS_B bit may be set accordingly.The LOS from a peak detector condition may also be reflected at thePLOSB output signal pin 350.

The optics control and status block 374 may be adapted to include atleast one OPRXLOS pin 376. The OPRXLOS input pin 376 in the opticscontrol and status block 374 may be utilized by an external opticalreceiver's LOS monitor to indicate when there is loss-of-lightcondition. The OPRXLOS pin 376, whether directly or in combination withthe peak detector logic, may be configured to force the CDR to lock tothe reference clock. A polarity of the OPRXLOS pin 376 may beprogrammable through one or more bits and/or registers. For example, anOPINLVL pin 378 may be adapted to control a OPINLVL bit in a PHYidentifier register. In accordance with an embodiment of the invention,the OPINLVL bit may be configured to change the polarity of OPRXLOS pin376.

The PMD CML serial inputs PDIP, PDIN 344 on the single-chip multimodemulti-sublayer PHY 130 may be AC-coupled. Advantageously, AC couplingmay prevent voltage drops across input devices of the single-chipmultimode sublayer PHY 130 when the input signals are sourced from ahigher operating voltage device. In a case where DC coupling is used, itmay be pertinent to ensure that input signals do not exceed certainV_(DD) levels. Additionally, it may be necessary to compensate for noisedue to overshoot and undershoot transients.

The PMD serial data stream may be deserialized to, for example, a 66-bitword format by, for example, a serial-to-parallel converter in the PMDTX/RX sublayer such as CDR and deserializer block 348. An output CDR anddeserializer block 348 may provide a clock signal necessary foroperation of the serial-to-parallel converter. Under normal operation,the CDR and deserializer block 348 may be configured to recover theclock from the data signal. If there is no data present, the clock maybe recovered from a reference clock such as an internal reference clock.The output of the CDR and deserializer block 348 may be sent to the RXGearbox 350 within PMD PCS sublayer. The RX Gearbox 350 may beconfigured to perform an equivalent function, albeit in reverse, as theTX Gearbox 328.

The output of the RX gearbox 350 may be coupled to a frame synchronizerdescrambler decoder block 352 embedded in the PMD PCS sublayer. The famesynchronizer function of the frame synchronizer descrambler decoderblock 352 may be configured to monitor and detect frame boundaries, forexample, a 66-bit frame boundary within the received data. The famesynchronizer function of the frame synchronizer descrambler decoderblock 352 may lock to 66-bit blocks using a sync header within the66-bit frame boundary. Once locked, the outputs of 66-bit data blocksmay be determined. The descrambler function of the fame synchronizerdescrambler decoder block 352 may be configured to process a payload forthe received data. In this regard, the descrambler function of the famesynchronizer descrambler decoder block 352, may utilize the samepolynomial employed by the scrambler function of the encoder scramblerblock 326, to reverse any effects of scrambling. Subsequently, thedecoder function of the fame synchronizer descrambler decoder block 352may decode the blocks of received data. In one aspect of the invention,the decoder may be configured to decode the blocks of received data inaccordance with the IEEE 802.3ae specification.

The output of the fame synchronizer descrambler decoder block 352 may becoupled to an elastic FIFO 354 located within the XGXS sublayer. Theoutput of the elastic FIFO 354 may be coupled to a randomizer 356located within the XGXS PCS sublayer. Randomizer 356 may be configuredto reduce EMI during an inter-packet gap (IPG). At least some of theresultant idle patterns at the XAUI transmitters may be repetitivehigh-frequency signals, which may be due, for example, to at least someof the 8B/10B encoders. The randomizer 356 may output random a randompattern, such as an IA/K/RI pattern, in one or more of the data lanesduring the IPG. The randomizer 356 may be configured to start itsrandomization processing on a column of the data containing, forexample, an end-of-packet (EOP) byte (T), and end on a SOP. In oneaspect of the invention, randomizer 356 may be adapted to utilize thepolynomial, 1+x³+x⁷ in compliance with the IEEE 802.3ae Draft 5.0standard.

The output of the randomizer 356 may be coupled to one or more encoders,for example, 8B/10B encoders 358, located within the XGXS PCS sublayer.The 8B/10B encoders 358 may be adapted so that each of 8B/10B encodersmay process a lane of data. In this case, the 8B/10B encoders 358 may beconfigured to convert a byte-wide data stream of random ones (1s) andzeros (0s) into, for example, a 10-bit DC-balanced serial stream of ones(1s) and zeros (0s). In one aspect of the invention, the DCbalancedserial stream of ones (1s) and zeros (0s) may have a maximum run lengthof about 6. Sufficient bit transitions may be provided, for example bysoftware, to ensure reliable clock recovery.

Each of the outputs of the 8B/10B encoders may be coupled to an input ofone or more serializers 360. In operation, data may be read out of the8B/10B encoder 358 using for example, an internally generated clock. Inone aspect of the invention, the internally generated clock may beconfigured to have a frequency of about 312.0-MHz clock. The data maythen be converted to, for example, a 3 Gigabit serial stream within XAUITX/RX sublayer and driven off-chip. Output pins XAOP, XAON, XDOP andXDON 362 may be configured to drive the output of serializers 360off-chip. In one aspect of the invention, bit zero (0) of frame zero (0)or the LSB may be shifted out first and may be mapped to “A” of the8B/10B encoder 358.

A XAUI CMU 346, which may be located within the XAUI TX/RX sublayer, mayinclude a PLL that may have the capability to generate a clock signalsuch as the 3 Gigabit clock. For example, XAUI CMU 346 may have thecapability of multiplying an internal 156.25 MHz reference clock togenerate the 3 Gigabit clock. The single-chip multimode multi-sublayerPHY 130 may also include a lock detect circuit. The lock detect circuitmay be configured to monitor a frequency of any internal VCO. In thisregard, a CMU lock detect bit may be configured to transition to a highstate whenever the XAUI CMU 346 PLL gets locked. The lock detect statusmay be indicated by one or more bits and/or registers, for example, bit7 of the ATSR.

The XAUI serial outputs, XAOP, XAON, XDOP, XDON 362 may be AC-coupledCML outputs. In this regard, the XAUI serial outputs, XAOP, XAON, XDOP,XDON 362 CML outputs may be powered by for example, by a +1.2V voltagesource. The XAUI serial outputs, XAOP, XAON, XDOP, XDON 362 may beadapted to be high-speed outputs and may include a differential pairdesignated to drive a 50Ω transmission line. The output driver may beback terminated to 50Ω on-chip resistor, which may provide snubbing ofany signal reflections. The output driver may also be configured topossess pre-emphasis capability that may enable it to compensate forfrequency selective attenuation of FR-4 traces. Advantageously, this mayeffectively compensate for any inter symbol interference (ISI) that mayoccur. The pre-emphasis capability may be controlled by one or more bitsand/or registers such as a XAUI pre-emphasis controller register.

In one embodiment of the invention, various interfaces of thesingle-chip XAUI transmit block 310 and receive block 340 may have thecapability to reverse the lane order and/or the lane polarity.Advantageously, XAUI I/O interface lane assignment package pins may bereversed to accommodate difficult PCB layouts. This capability may becontrolled via one or more bits or registers such as a XAUI digitalcontrol register. In one aspect of the invention, a lane flipper may beconfigured to perform a byte-wise flip of any internal lane data. Thismay include, but is not limited to, 32-bit data. By default, lane “A”may be configured to carry byte zero (0), lane “B” may be configured tocarry byte one (1), lane “C” may be configured to carry byte two (2),and lane “D” may be configured to carry byte three (3).

In another embodiment of the invention, whenever the lane flipper isenabled, lane “A” may be configured to carry byte three (3), lane “B”may be configured to carry byte two (2), lane “C” may configured tocarry byte one (1), and lane “D” may be configured to carry byte zero(0). In this regard, reversal of the lanes may be achieved by settingone or more bits and/or registers. For example, a bit such as aXAUI_TX_FLIP_B and a XAUI_RX_FLIP_B which may be located in a XAUIdigital control register in the management registers and controlinterface block 372, may be set or cleared in order to reverse the XAUIlane order.

In yet a further embodiment of the invention, one or more XAUI I/Ointerface bit assignment (P to N) to package pins may be reversed inorder to accommodate difficult PCB layouts. Assert bits such as aXAUI_TZ_INV and a XAUI_RX_INV bit, which may be located in a XAUIdigital control register in the management registers and controlinterface block 372, may be set or cleared in order to reverse the XAUIlane polarity.

In accordance with the invention, the single-chip multimodemulti-sublayer PHY 130 may be configured to support asynchronousclocking mode operation of the XAUI and PMD interfaces. The localreference clock or external transmit VCXO may be adapted to function inaccordance with the IEEE specifications. In this regard, one or moreelastic FIFO buffers may be configured to be an integral part of theasynchronous operation mode. For example, receive block 340 may includeone or more elastic FIFOs 354 and the transmit block 310 may include oneor more elastic FIFOs 324. The elastic FIFOs 354, 324 may be configuredto accommodate a frequency difference of up to 200 ppm between arecovered clock and a local reference clock. The elastic FIFOs 354, 324may have read and write pointers, which may be used for data access andmanipulation. The Idle columns of data may be inserted or deleted duringthe IPG once the distance between the elastic FIFO's read and writepointers exceed a given threshold. In accordance with one aspect of theinvention, idle columns of four bytes of data may be inserted or deletedduring the IPG. In addition, a column of sequence orders may be deletedduring the IPG once the distance between the elastic FIFO's read andwrite pointer exceed a threshold. In accordance with another aspect ofthe invention, the delete adjustments may occur on IPG streams thatcontain at least two columns of idles or sequence order sets.

FIG. 4 is a plot 400 illustrating a frequency response of an exemplarycommunication signal communicated over a high-speed network. In general,communication signals may become attenuated as they traverse acommunication media or network. In this regard, the high frequencycomponents of the communication signal may be attenuated more than lowerfrequency signal components. In typical high-speed communicationsystems, the amplitude of the received signal component may beattenuated proportionally to the square root of the signal frequency.Accordingly, FIG. 4 graphs this attenuation characteristic.

FIG. 5 is a plot 500 illustrating a typical equalization profile thatmay be utilized to equalize an attenuated communication signal. In orderto minimize or compensate for the high frequency attenuation effect,existing high-speed data receivers provide an equalization element. Theequalization element may be configured to amplify the incoming signal sothat the higher frequency signal components may be amplified to agreater degree than the lower frequency signal components. Referring toFIG. 5, the higher frequency components may be amplified more than thelower frequency components. Notably, while higher frequency componentsreceive a greater degree of amplification, the lower frequencycomponents may also be amplified. Equalizing the input signal in thismanner generally results in a signal that is strong across allfrequencies that may comprise the signal. FIG. 6 is a plot 600 of aillustrating the increase in signal amplitude across frequencycomponents that may comprise the signal.

In general Ethernet-based systems do not exhibit as much high frequencysignal attenuation as Fibre Channel systems. Since Ethernet and FibreChannel systems exhibit different signal attenuation characteristics,certain difficulties may arise in devices PHY devices that may implementboth Ethernet and Fiber channel within a single transceiver. In thisregard, multimode mode devices such as the single-chip multimodemulti-sublayer PHY 130 may require an optimal equalization processingelement that may facilitate both Ethernet and fiber channel modes ofoperation.

FIG. 7 a is a block diagram of an exemplary signal equalization element700 according to an embodiment of the present invention. Referring toFIG. 7 a, equalization element 700 may include a signal divider 704, alow frequency gain stage 702, an equalization stage 706 and a summingelement 708. The signal divider 704 may be a programmable signaldivider. The equalization element 700 may be integrated within the PMDreceive section or the PMD TX/RX sublayer of the single-chip multimodemulti-sublayer PHY 130. In one embodiment of the invention, theequalization element 700 may be integrated within a limiting amplifierof the PMD receive section of the single-chip multimode multi-sublayerPHY 130.

The signal divider 704 may be configured to receive, for example, a 10Gbps input signal and apportion or divide the signal according to aselect signal 710. In an illustrative embodiment of the presentinvention, the select line 710 may be a 3-bit select line, therebyproviding eight select levels. Preferably, the select line 710 may be ann-bit select line, thereby providing 2^(n) select levels. In thisregard, n may define a resolution of the signal divider 704 and maycontrol apportionment of the input signal to the low frequency gainstage 702 and the equalization stage 706.

The signal divider 704 may be configured to divide the input signal andsend a portion of the input signal to the low-frequency gain stage 702and a portion of the input signal to the equalization stage, dependingon the select level indicated by the select line 710. The select line710 may be configured to indicate that all of the input signal should besent to the low-frequency gain stage 702 or the equalization stage 706.In a case where the select line 710 may be configured to send all of theinput signal to the low frequency gain stage 702, then none of the inputsignal may be sent to the equalization stage 706. In a case where theselect line 710 may be configured to send the entire input signal to theequalization stage 706, then none of the input signal may be sent to thelow frequency gain stage 702. Depending on the resolution of the signaldivider 704, various levels of the input signal may be sent to the lowfrequency gain stage 702 and/or the equalization stage 706.

In accordance with one embodiment of the invention, if the 3-bit selectline has a binary value of 000, all of the input signal may be providedto the low-frequency gain stage 702 and none of the input signal isprovided to the equalization stage 706. If the 3-bit select line has abinary value of 111, a large portion of the incoming signal, andpossibly the entire input signal may be provided to the equalizationstage 706. Additionally, a small portion of the input signal andpossibly none of the input signal may be provided to the low-frequencygain stage 810. Select values that may occur between 000 and 111 mayapportion the input signal between the low-frequency gain stage 702 andthe equalization stage 706. In one aspect of the invention, the lowerthe select value, the greater the percentage of the input signal thatmay be sent to the low-frequency gain stage 704. Accordingly, the higherthe select value, the greater the percentage of the input signal thatmay be sent to the equalization stage 706.

In operation, the low-frequency gain stage 702 may be adapted to equallyamplify all low frequency components. These frequency components maycomprise that portion of the input signal that the signal divider 704may apportion to be directed to the low-frequency gain stage 702. Theequalization stage 706 may be adapted to amplify at least a portion ofhigher frequency components. These frequency components may comprisethat portion of the input signal that the signal divider 704 mayapportion to be directed to the equalization stage 706. In this regard,the equalization stage 706 may amplify the higher frequency componentsof the input signal to a greater degree than lower frequency components.The equalization processing carried out by the equalization stage 706may be done in a manner similar to that illustrated in FIG. 5.Subsequently, the summing element 708 may be adapted to sum the variousoutputs of the low-frequency gain stage 702 and the equalization stage706 to produce an equalized output signal 712.

In another embodiment of the invention, an equalization element having aflat gain stage and a high pass filter stage may be provided. FIG. 7 bis an exemplary block diagram of an equalization element 750 thatutilizes a flat gain stage and a high pass filter stage in accordancewith an embodiment of the invention. Referring to FIG. 7 b, equalizationelement 750 may include a flat gain stage 752, a high pass filter gainstage 756, a control block 754 and a summing element 758. Theequalization element 750 may be integrated within the PMD receivesection or the PMD TX/RX sublayer of the single-chip multimodemulti-sublayer PHY 130. In one embodiment of the invention, theequalization element 750 may be integrated within a limiting amplifierof the PMD receive section of the single-chip multimode multi-sublayerPHY 130. The control block 750 may be any suitable controller, processorand/or circuitry that may be adapted to control the flat gain stage 752and the high pass filter gain stage 756

In operation, the flat gain stage 752 may be adapted to equally amplifyat least a portion of the low frequency components. The high pass filtergain stage 756 may be adapted to amplify at least a portion of higherfrequency components. In this regard, the equalization stage 756 mayamplify the higher frequency components of the input signal to a greaterdegree than lower frequency components. Control block 754 may be adaptedto independently control the gain of the flat gain stage 752 and thegain of the high pass filter gain stage 756. In this regard, the gain ofthe low frequency components and the high frequency components may beseparately controlled. The equalization element 750 of FIG. 7 b mayachieve a function equivalent to that illustrated in FIG. 7 b withoutimplementing a signal divider block 704. The summing element 758 may beadapted to sum the various outputs of the flat gain stage 752 and thehigh pass filter gain stage 756 to produce an equalized output signal762.

FIG. 8 is a plot 800 illustrating exemplary equalization profilesaccording to an embodiment of the invention. Referring to FIG. 8, plot800 may include curves 802 and 804. Curve 802 may be the resultantequalization profile for selection of only the equalization stage 706(FIG. 7). In an illustrative embodiment, the resultant equalizationprofile depicted by curve 802 may be selected exclusively for Fibrechannel operation mode. In that case, a receiver or transceiver mayoperate exclusively in a Fibre channel mode. Curve 804 may be theresultant profile for selection of only the low-frequency gain stage 702(FIG. 7). In an illustrative embodiment, the resultant equalizationprofile depicted by curve 804 may be selected exclusively for 10 GbEoperation mode. In a case where n=3, the signal divider 704 may becontrolled by a 3-bit select signal. Accordingly, the select value 000may be used to select an equalization profile, which may represent anexclusive Fibre channel operation mode. The select value 111 may be usedto select an equalization profile, which may represent an exclusive 10GbE operation mode. Other intermediate equalization profiles,corresponding to 3-bit select values 001–110, may lie between curves 802and 804.

FIG. 9 is plot 900 for exemplary equalization profiles in accordancewith an embodiment of the invention. Referring to FIG. 3, there areillustrated equalization profiles curves 902, 916, 914, 912, 910, 908,906, and 904. In this exemplary case, n=3, and the exclusive Fibrechannel operation mode may utilize select bit value 000, which may berepresented by curve 904. The exclusive 10 GbE operation mode mayutilize select bit value 111, which may be represented by equalizationprofile curve 902. The equalization profiles curves 916, 914, 912, 910,908, 906 may be represented by bit select 110, 101, 100, 011, 010, and001, respectively. Equalization profiles curves 916, 914, 912, 910, 908,906 may represent intermediate operations for various combinations of 10GbE and Fibre channel modes of operation. Accordingly, depending on aparticular characteristic of a combination of operation modes, anappropriate intermediate equalization profile may be selected.

It should be recognized that the invention is not limited to a value ofn=3, but n may preferably have a value which may be greater than orequal to (≧) two (2). In a case where n=1, then only an exclusive 10 GbEoperation mode or an exclusive Fibre channel operation mode may beprovided, and there may be no intermediate operational modes. In thisregard, zero (0) may represent the exclusive 10 GbE operation mode anone (1) may represent an exclusive Fibre channel operation mode.Alternatively, one (1) may represent the exclusive 10 GbE operation modean zero (0) may represent an exclusive Fibre channel operation mode.

In an alternative embodiment of the present invention, the entire inputcommunication signal may be provided to both the low-frequency gainstage 702 and the equalization stage 706, rather than apportioning theinput signal in accordance with the arrangements previously described.Accordingly, the select values may determine how much gain may beprovided by the low-frequency gain stage 702 and the equalization stage706. In an illustrative embodiment of the invention, in a case wheren=3, if the 3-bit select value is 000, the low-frequency gain stage 702of the equalization element 700 may be configured to provide a highamount of gain, while the equalization stage may be configured toprovide a lesser or no amplification to the input signal. If the 3-bitselect value is 111, the equalization stage 704 may be configured toprovide a high degree of amplification, while the low-frequency gainstage 702 may provide a lesser or no gain to the input signal. Selectvalues 001–110 may provide varying intermediate levels or degrees ofamplification by the two stages.

In one embodiment of the invention, the signal divider 704 may beadapted to operate as a splitter. In this regard, the input signal maybe split by the signal divider 704 so that the entire input signal maybe provided to both the low-frequency gain stage 702 and theequalization stage 706, rather than being apportioned. In this regard,both low frequency and high frequency components of the input signal maybe provided to the low-frequency gain stage 702 and the equalizationstage 706. Accordingly, a particular select value may be utilized toadapt the signal divider 704 to operate as a splitter. For example, aselect value of 100 may be appropriated to configure the signal divider704 to operate as a splitter. The select signal 704 may be coupleddirectly to the low-frequency gain state 702 and the equalization stage706 of the equalization element 700.

In a further aspect of the invention, one or more bits and/or registersmay be configured to control the select signal 710. For example, MDIOpin 380 may be coupled to the select signal 710. In this arrangement,one or more bits and/or registers in the management registers andcontrol interface block 372 (FIG. 3) of the single-chip multimodemulti-sublayer PHY 130, may be programmed with the select values. Theselect value may be programmed to a default value, for example duringmanufacturing. The select value may also be reprogrammed at any time,for example during initialization or operation, in order to effect adifferent equalization and low-frequency gain combination. In thisregard, the single-chip multimode multi-sublayer PHY 130 may have acapability to adaptively select an optimal combination of signalequalization and low frequency gain.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in one computersystem, or in a distributed fashion where different elements are spreadacross several interconnected computer systems. Any kind of computersystem or other apparatus adapted for carrying out the methods describedherein is suited. A typical combination of hardware and software may bea general-purpose computer system with a computer program that, whenbeing loaded and executed, controls the computer system such that itcarries out the methods described herein.

The present invention also may be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

Notwithstanding, the invention and its inventive arrangements disclosedherein may be embodied in other forms without departing from the spiritor essential attributes thereof. Accordingly, reference should be madeto the following claims, rather than to the foregoing specification, asindicating the scope of the invention. In this regard, the descriptionabove is intended by way of example only and is not intended to limitthe present invention in any way, except as set forth in the followingclaims.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for adjusting at least one of a gain and a frequencyresponse of an input signal for a multimode PHY device, the methodcomprising: after receipt of the input signal, apportioning the inputsignal into at least a gain adjustment signal and at least anequalization adjustment signal; adjusting a gain of said apportioned atleast a gain adjustment signal within the multimode PHY device;equalizing said at least an equalization adjustment signal within themultimode PHY device; and summing said adjusted at least a gainadjustment signal and said equalized at least an equalization adjustmentsignal within the multimode PHY device to create an output equalizedsignal having a desired gain and frequency response.
 2. The methodaccording to claim 1, wherein, said apportioned at least a gainadjustment signal comprises low frequency components of the inputsignal; and said apportioned at least an equalization adjustment signalcomprises high frequency components of the input signal.
 3. The methodaccording to claim 2, wherein said apportioning comprises selecting adetermined portion of said input signal that will comprise said at leasta gain adjustment signal and said at least an equalization signal. 4.The method according to claim 3, wherein said determined portion of saidinput signal is one of a whole of the input signal and a fraction of theinput signal.
 5. The method according to claim 3, wherein said adjustingcomprises programmably selecting said determined portion of said inputsignal that will comprise said at least a gain adjustment signal andsaid at least an equalization signal.
 6. The method according to claim2, wherein said adjusting comprises amplifying said gain of at leastsome of said low frequency components of said apportioned at least again adjustment signal.
 7. The method according to claim 6, wherein saidamplifying comprises equally amplifying said gain of at least some ofsaid low frequency components of said apportioned at least gainadjustment signal.
 8. The method according to claim 2, wherein saidequalizing comprises amplifying said gain of at least some of said highfrequency components of said apportioned at least an equalizationadjustment signal.
 9. The method according to claim 1, wherein the inputsignal comprises signal components from at least one of a 10 GigaBitEthernet operation mode and a Fibre channel operation mode.
 10. Themethod according to claim 1, wherein said apportioning comprisesapportioning said input signal so that said at least a gain adjustmentsignal and said at least an equalization adjustment signal areequivalent to the input signal.
 11. A system for adjusting at least oneof a gain and a frequency response of an input signal for a multimodePHY device, the system comprising: a signal divider for apportioning theinput signal into at least a gain adjustment signal and at least anequalization adjustment signal; a signal adjuster for adjusting a gainof said apportioned at least a gain adjustment signal within themultimode PHY device; an equalizer for equalizing said at least anequalization adjustment signal within the multimode PHY device; and asummer for summing said adjusted at least a gain adjustment signal andsaid equalized at least an equalization adjustment signal within themultimode PHY device to create an output equalized signal.
 12. Thesystem according to claim 11, wherein, said apportioned at least a gainadjustment signal comprises low frequency components of said inputsignal; and said apportioned at least an equalization adjustment signalcomprises high frequency components of said input signal.
 13. The systemaccording to claim 12, wherein said signal divider comprises a selectorfor selecting a determined portion of said input signal that willcomprise said at least a gain adjustment signal and said at least anequalization adjustment signal.
 14. The system according to claim 13,wherein said selector is configured to select said determined portion ofsaid input signal that is one of a whole of the input signal and afraction of the input signal.
 15. The system according to claim 14,wherein said adjuster comprises a programmable selector for programmablyselecting said determined portion of said input signal that willcomprise said at least a gain adjustment signal and said at least anequalization adjustment signal.
 16. The system according to claim 12,wherein said adjuster comprises an amplifier for amplifying said gain ofat least some of said low frequency components of said apportioned atleast a gain adjustment signal.
 17. The system according to claim 12,wherein said adjuster comprises an amplifier that is configured toequally amplify said gain of at least some of said low frequencycomponents of said apportioned at least a again adjustment signal. 18.The system according to claim 12, wherein said equalizer comprises anamplifier for amplifying said gain of at least some of said highfrequency components of said apportioned at least an equalizationadjustment signal.
 19. The system according to claim 11, wherein theinput signal comprises signal components from at least one of a 10Gigabit Ethernet operation mode and a Fibre channel operation mode. 20.The system according to claim 11, wherein said signal divider comprisesan apportioner for apportioning said input signal so that said at leastgain adjustment signal and said at least an equalization adjustmentsignal are equivalent to the input signal.
 21. The system according toclaim 20, comprising a selector for selecting a level of adjustment tobe applied to said at least a gain adjustment signal and said at leastan equalization adjustment signal.
 22. The system according to claim 21,wherein said selector is coupled to at least one device selected fromthe group consisting of said apportioner, said signal divider, saidsignal adjuster and said equalizer.
 23. A method for adjusting at leastone of a gain and a frequency response of an input signal for amultimode PHY device, the method comprising: after receipt of the inputsignal, adjusting a gain of at least a portion of the input signalwithin the multimode PHY device; equalizing at least a remaining portionof the input signal within the multimode PHY device; and summing saidadjusted at least a portion of the input signal and said equalized atleast a remaining portion of the input signal within the multimode PHYdevice to create an output equalized signal having a desired gain andfrequency response.
 24. The method according to claim 23, wherein, saidadjusted at least a portion of the input signal comprises low frequencycomponents of the input signal; and said equalized at least a remainingportion of the input signal comprises high frequency components of theinput signal.
 25. The method according to claim 24, wherein saidadjusting comprises amplifying said gain of at least a portion of saidlow frequency components.
 26. The method according to claim 24, whereinsaid adjusting comprises equally amplifying said gain of said at least aportion of said low frequency components.
 27. A system for adjusting atleast one of a gain and a frequency response of an input signal for amultimode PHY device, the system comprising: at least one adjusteradapted to adjust a gain of at least a portion of the input signalwithin the multimode PHY device; at least one equalizer adapted toequalize at least a remaining portion of the input signal within themultimode PHY device; and at least one summer adapted to sum saidadjusted at least a portion of the input signal and said equalized atleast a remaining portion of the input signal within the multimode PHYdevice to create an output equalized signal having a desired gain andfrequency response.
 28. The system according to claim 27, wherein, saidadjusted at least a portion of the input signal comprises low frequencycomponents of the input signal; and said equalized at least a remainingportion of the input signal comprises high frequency components of theinput signal.
 29. The system according to claim 28, wherein saidadjuster comprises at least one controller adapted to controlamplification of said gain of at least a portion of said low frequencycomponents.
 30. The system according to claim 28, wherein said adjustercomprises at least one controller that is adapted to control equalamplification of said gain of said at least a portion of said lowfrequency components.
 31. The system according to claim 28, wherein saidat least one controller is further adapted to control amplification ofsaid at least a portion of said high frequency components of the inputsignal.
 32. The system according to claim 28, wherein said at least onecontroller is further adapted to control adjustment of said at least aportion of said high frequency components of the input signalindependent of said at least a portion of said low frequency components.33. The system according to claim 27, wherein the input signal comprisessignal components from at least one of a 10 GigaBit Ethernet operationmode and a Fibre channel operation mode.